System and method for remediation of explosive contamination using convective heat

ABSTRACT

According to the present teachings, a system and method are provided for decontaminating a conduit or vessel contaminated with residual explosive material. The system can include a heated gas flow source for heating a gas and providing a flow of the heated gas into the interior of a conduit or vessel. The temperature of the heated flow of gas can be at or in excess of the break down temperature of the residual explosive material.

INTRODUCTION

The present teachings relate to a system and method for decontaminatinga sewer line or other conduit, or a storage tank or other vessel,contaminated with residual explosive material.

SUMMARY

According to various embodiments, a system is provided that can comprisea conduit such as a sewer line, or a vessel such as a storage tank,having an inner surface comprising residual explosive material depositedthereon, and a heated gas flow source in fluid communication with theinner surface. The residual explosive material can have a break downtemperature, and the heated gas flow source can be adapted to produce aflow of heated gas into the conduit or vessel sufficient to heat theinner surface to a temperature at or in excess of the break downtemperature.

According to various embodiments, a system is provided that can comprisea heated gas flow source. The heated gas flow source can comprise one ormore burner units. The heated gas flow source can comprise one or morefan or blower units in communication with one or more burner units andcan be adapted to introduce gas, heated by the burner unit, into a sewerline at a flow rate. The heated gas flow source can comprise a fuelsource. When the fuel source is a liquid, the heated gas flow source cancomprise a vaporizer in communication with the fuel source and theburner unit. The vaporizer can be adapted to receive liquid fuel fromthe fuel source, vaporize the liquid fuel to produce a gas fuel, andprovide the gas fuel to the burner unit.

According to various embodiments, a method is provided that cancomprise: connecting a heated gas flow source to a conduit or vesselcomprising residual explosive material deposited on an inner surfacethereof, the residual explosive material having a break down temperatureat which the residual explosive material chemically decomposes or breaksdown; introducing a heated gas flow into the conduit or vessel; andmaintaining a flow of heated gas through the conduit or vessel until thetemperature of the inner surface reaches a temperature at or in excessof the break down temperature of the residual explosive material.

According to various embodiments, the method according to the presentteachings can comprise maintaining the internal surface of a conduit orvessel at or in excess of the break down temperature of a residualexplosive material or materials, for a period of time. The period oftime can be, for example, one minute or longer, 10 minutes or longer, or30 minutes or longer.

According to various embodiments, the method according to the presentteachings can comprise maintaining the internal surface of a conduit orvessel at or in excess of the break down temperature of a residualexplosive material or materials deposited therein, for a period of timethat can comprise a period of time sufficient to ensure break down ofthe residual explosive material or materials.

According to various embodiments, the method according to the presentteachings can comprise providing a heated gas flow at an initialtemperature to a conduit or vessel comprising an inlet, an outlet, andan interior surface comprising residual explosive material having abreak down temperature, deposited thereon, wherein the interior surfaceis in fluid communication with the heated gas flow, and maintaining theheated flow of gas at or above the initial temperature at least untilthe temperature of the heated flow of gas at the outlet is at or abovethe break down temperature of the residual explosive material.

Additional features and advantages of the present teachings are setforth in part in the description that follows, and in part will beapparent from the description, or may be learned by practice of thepresent teachings. The objectives and other advantages of the presentteachings will be realized and attained by means of the elements andcombinations particularly pointed out in the description that follows.

It is to be understood that both the foregoing summary and the followingdescription are exemplary and explanatory only and are intended toprovide a further explanation of the present teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present teachings are exemplified in theaccompanying drawings. The teachings are not limited to the embodimentsdepicted in the drawings, and include equivalent structures and methodsas set forth in the following description and as would be known to thoseof ordinary skill in the art in view of the present teachings. In thedrawings:

FIG. 1 illustrates a heated gas flow source connected to a sewer line inaccordance with various embodiments of the present teachings;

FIG. 2 is a graph illustrating temperatures recorded by thermocouplesduring a convective heat decontamination method according to variousembodiments of the present teachings;

FIG. 3 illustrates a graph of the temperatures reached during aconvective heat decontamination method according to various embodimentsof the present teachings.

DESCRIPTION

Definitions: The below definitions serve to provide a clear andconsistent understanding of the present teachings.

The term “break down” is herein defined as the temperature at which aparticular residual explosive material chemically decomposes or breaksdown and is no longer explosive or otherwise volatile. The break downtemperature of the explosive material is the temperature at which achemical change in the composition of the explosive material occurs, forexample, the temperature at which the explosive material ignites,combusts, explodes, deflagrates, oxidizes, reduces, decomposes, orotherwise breaks down.

The term “heated gas flow source” is herein defined as any device orcombination of devices, capable of producing a heated flow of gas. Theheated gas flow source can comprise a heating unit. The heating unit cancomprise a gas burner, an electrical device, a solar heater, a lightemitting device, or a combination thereof. A gas burner can comprise apropane burner, for example, a conventional propane burner. A propaneburner can comprise a tube-type burner. The heated gas flow source cancomprise a blower unit, for example a centrifugal blower. The heated gasflow source can comprise a vaporizer. The burner unit, blower unit andvaporizer, can each be a separate device, or any two of or all three of,the burner unit, blower unit and vaporizer, can be provided in a singledevice.

The term “heated flow of gas” is herein defined as a flow of gas at atemperature above ambient temperature. The heated flow of gas cancomprise an initial temperature which can be increased to a targettemperature. The heated flow of gas can comprises a temperaturesufficient to break down one or more residual explosive materials. Theheated flow of gas can comprise a temperature and flow rate sufficientto break down one or more residual explosive materials. The flow of gascan comprise a heated flow of gas provided at sufficient temperature, asufficient flow rate, and for a sufficient time, to break down one ormore residual explosive materials. The flow of gas can be introducedinto a conduit or vessel at atmospheric pressure or greater.

The heated flow of gas can comprise a positive-pressure mediated flow ofheated gas where the heated flow of gas is introduced into the conduitor vessel at a pressure greater than one atmosphere. The gas of theheated flow of gas, can comprise, for example, air, combustion products,or a combination thereof. The term “heated gas flow” is usedsynonymously with the term “heated flow of gas” as defined herein.

The term “internal surface” is herein defined as the entire interiorsurface of a conduit, for example, a sewer line, or a vessel, forexample, an aboveground or underground storage tank. The internalsurface can comprise the interior surface only, or can comprise theinterior surface and a thickness of the conduit or vessel wall. Aninterior surface including a wall thickness can comprise a region fromthe interior surface to a depth of up to 0.5 inch into the material ofthe wall. The depth can comprise a depth of from about greater than 0inch to about three inches, a depth of from about greater than 0 inch toabout 0.5 inch, a depth of from about greater than 0 inch to about 0.25inch, or a depth of about 0.25 inch. In the case where the wall of theconduit or sewer line comprises a porous material, the internal surfacecan comprise a thickness, for example, to ensure that any residualexplosive material penetrating the porous interior surface is completelydecomposed or broken down during convective heat treatment.

The term “residual explosive material” is herein defined as any materialhaving explosive properties. Such residual materials can comprise one ormore of nitroguanidine, dinitrotoluene (DNT), trinitrotoluene (TNT),hexogene, octogene, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX),Pentaerythritol tetranitrate (PETN), cyclotetramethylene-tetranitramine(HMX), tetryl, nitrocellulose (NC), nitroglycerine (NG), ammoniumnitrate, lead azide, lead styphnate, and a combination thereof.

The term “conduit or vessel” is herein defined as any structure used tocarry a material from a source to a disposal site. The conduit or vesselcan comprise a storm water drain line, a sewer line, an industrial wasteline, a sanitary waste line, or a pipe. A conduit or vessel can compriseany material capable of maintaining thermal stability or remainingintact, at a temperature at or in excess of, a residual explosivematerial's break down temperature. For example, the conduit or vesselmaterial can comprise one or more of terracotta, concrete, brick, monel,and a combination thereof.

The term “source of alkane” is herein defined as any alkane source. Analkane source can comprise one or more of ethane, propane, butane,pentane, hexane, heptane, octane, and a combination thereof. The term“alkane source” is used synonymously with the term “source of alkane” asdefined herein.

The term “initial temperature” is herein defined as the temperature atwhich a heated flow of gas is first introduced into a conduit or vessel.The initial temperature can comprise a target gas flow temperature.

The term “target gas flow temperature” is herein defined as a gas flowtemperature of the gas flow entering the gas inlet at or above theinitial temperature that is sufficient to achieve break down of aresidual explosive material. The target gas flow temperature can be ator in excess of the break down temperature of any residual explosivematerial present in a conduit or vessel being decontaminated.

According to various embodiments, the present system and method providesfor break down of residual explosive material using convective heatwhere a source of heat energy is placed at one end of a section of aconduit or vessel, hereforth exemplified as a sewer line, while a blowerpushes heated gas, for example, heated air, through the sewer line toheat up the sewer line including the internal surface of the sewer line.The system can be operated for a time and at a temperature, sufficientto achieve decomposition or break down of residual explosive materialdeposited in or on the internal surface.

According to various embodiments, the heated flow of gas is provided ata temperature, a flow rate, and for a time period, sufficient to heat aninternal surface of a length of sewer line to a target temperature at orin excess of the break down temperature of one or more residualexplosive materials. Once the internal surface of the sewer line is ator above the break down temperature, the heated flow of gas can bemaintained at the target temperature for period of time sufficient toensure complete break down of the residual explosive material, forexample, for about 2.0 hours or more.

Thermal properties of common explosives are shown in the table below.The break down temperatures discussed herein with respect to suchexplosives as shown in the table, can be understood, for example, as the“deflagration temperature.” TABLE I THERMAL PROPERTIES OF COMMONEXPLOSIVES Material Melting Point Deflagration Temperature Tri NitroToluene 178° F. 537°-572° F.    Hexahydro-1,3,5-Trinitro- 392° F. 500°F. 1,3,5-Triazine Pentaerythritol Tetranitrate 286° F. 394° F.Nitro-Gylcerine 56.3° F.  432° F. Nitrocellulose 275° F. 338° F.

According to various embodiments, and in view of the break downtemperatures of residual explosive materials, in the event that a sewerline is contaminated with explosive materials, where the composition ofthe explosive material is not known, decontamination of the sewer linecan be achieved by heating the inner surface of the sewer line to at orin excess of the break down temperature of TNT, i.e., at or in excess of572° F., according to various embodiments of the present teachings.

According to various embodiments, the convective heating method cancomprise discharging combustion products of a gas burner into an openingof a section of a sewer line while a blower induces a gas flow throughthe sewer line from the opening of the section. The temperature of theexhaust gas leaving an opposite end or section of the sewer can bemeasured and recorded. As the interior of the sewer line is heated, theexhaust temperature rises. When the exhaust temperature reaches thedesired break down temperature, for example, 572° F. or greater, theburner can continue to be fired for a given period of time (“soak” time)and at a rate sufficient to maintain this temperature, for example, forabout 2 hours. Thereafter, the burner can be shut down and the blowercan be turned off. The sewer line can then be allowed to cool downslowly through conduction to the material surrounding the sewer line,for example, to the surrounding soil or atmosphere.

A gas burner can be used to combust a fuel to produce the heated gas,for example, to produce heated air. A fuel source can comprise one ormore liquid or vapor fuels. A vapor fuel can comprise one or morevaporized liquid fuels. A liquid fuel can comprise one or more alkanesincluding for example, one or more of ethane, propane, butane, pentane,hexane, heptane, octane, and a combination thereof.

The gas burner unit can comprise a sensor capable of detecting theabsence of a flame, for example, if the flame goes out, the supply offuel would automatically cut-off. Suitable sensors can comprise anultraviolet sensor or a bimetallic switch.

The method can comprise vaporizing a liquid gas fuel source using avaporizer. The vaporized fuel source, for example, vaporized propane,can then be provided to the burner unit, for example, a propane burner.The vaporizer can be part of the burner unit, or can be a deviceprovided separate from the burner unit. The vaporizer can comprise aliquid bath vaporizer.

Ignition of the vaporized gas can comprise ignition using a spark plugtype of ignition device, for example an ignition wire. Other suitableignition devices can include a lighter or an electric match. Otherignition devices are known and can be readily selected and employed byone of ordinary skill in the art to which the present teachings pertain,without undue experimentation.

One or more burner units can be used to heat a gas, for example, air, toa desired temperature. The heated air can then be blown into a sewerline using one or more blower units, through at least one gas inlet. Theheated gas can be introduced into the sewer line through two or more gasinlets. The gas inlet can comprise an existing opening in the sewerline, for example an opening in a street through a drain or a manhole,or can comprise a break made in the sewer line for the purpose ofaccessing the sewer line.

The heated gas flow source can be connected to the gas inlet by anymeans sufficient to provide a seal between the heated gas flow sourceand an opening in the sewer line being decontaminated. A seal can beprovided, for example, by fitting the heated gas flow source into anopening in a sewer line and sealing the heated gas flow source withmineral wool. The heated gas flow source can be fitted into the openingin the sewer line via any means capable of withstanding temperatures ator in excess of a desired target temperature. For example, the heatedgas flow source can be fitted into an opening in a sewer line via a ductor a hose, for example a flexible hose. Similar fittings can be used forother conduits or vessels.

The blower unit can be part of the burner unit or can be a unit separatefrom the burner unit. The heated gas can be continually blown into thesewer line through one or more gas inlets, the heated gas then travelsthe length of the sewer line, and exhausts the sewer line through one ormore gas outlets. The temperature of the heated gas can be monitored at,at least the gas inlet and the gas outlet, using temperature sensors,which sensors can comprise a thermocouple. The temperature of the sewerline can be monitored at, for example, the inner surface, the innersurface to a depth of about 0.25 to about 0.5 inch, and/or the outersurface or skin of the sewer line.

A blower unit can comprise, for example, a centrifugal blower, a fanunit, a turbine, or the like. According to various embodiments, theblower unit can be connected to the burner end of the burner unit via aduct. A duct can comprise a flexible hose. A flexible hose can comprisea reinforced, flexible hose. The reinforced, flexible hose can comprisea spiral-reinforced, flexible hose.

According to various embodiments, during operation, heated gas can begenerated by the burner unit. The burner unit can discharge the heatedgas into the opening of a section of a sewer line while one or moreblower units can induce flow of the heated gas through the sewer linefrom the opening section via one or more gas inlets.

When the sewer line comprises a material, for example terracotta, thatis susceptible to thermal shock, for example, as evidenced by crackingor collapse due to a rapid increase in temperature, the heated gas canbe initially supplied to the opening section at an initial temperaturebelow the break down temperature of any residual explosive materialpresent in the sewer line being decontaminated. The initial temperaturecan comprise a temperature of less than about 400° F., of less thanabout 300° F., of less than about 200° F., of from about 100° F. toabout 300° F., of from about 125° F. to about 225° F., or of about 150°F. The temperature of the heated gas can be increased slowly in order toavoid thermal shock to the sewer line, for example, in order to avoidcracking of the sewer line.

The initial temperature can be increased slowly to a target gas flowtemperature, for example, the initial temperature can be increased at arate of from about 1.5° F./min to about 10.0° F./min., of from about2.0° F./min to about 8.0° F./min., of from about 2.5° F./min to about6.0° F./min., of from about 3.0° F./min to about 5.0° F./min., or offrom about 3.5° F./min to about 4.5° F./min.

The target gas flow temperature can be a temperature at or in excess ofa break down temperature of one or more explosive materials present inthe sewer line being decontaminated. Depending on the residual explosivematerial or materials present, the target temperature can be greaterthan about 400° F., greater than about 500° F., greater than about 572°F., greater than or equal to about 572° F., of from about 400° F. toabout 3,000° F., of from about 500° F. to about 3,000° F., of from about572° F. to about 3,000° F., of from about 600° F. to about 3,000° F., offrom about 700° F. to about 3,000° F., of from about 900° F. to about3,000° F., of from about 1,000° F. to about 3,000° F., of from about1,500° F. to about 3,000° F., of from about 2,000° F. to about 3,000°F., or of from about 2,200° F. to about 3,000° F.

For sewer line materials susceptible to thermal shock, for example,terracotta, the heated gas can be introduced into the sewer line at aninitial temperature that can be slowly increased until a target gas flowtemperature is achieved. The time necessary to achieve an increase intemperature from the initial temperature to the target temperature candepend on the rate of temperature increase, and can comprise a period oftime of from about 1.0 hour to about 8.0 hours, of from about 1.5 hoursto about 8.0 hours, of from about 2.0 hours to about 6.0 hours, of fromabout 2.0 hours to about 5.0 hours, of from about 2.5 hours to about 4.0hours, of from about 2.0 hours to about 3.5 hours, or of from about 2.0hours to about 3.0 hours.

For sewer line materials not susceptible to thermal shock, the heatedgas flow can be introduced into the sewer line as described above formaterials susceptible to thermal shock, or the heated gas flow can beintroduced at about the target gas flow temperature.

According to various embodiments, once the heated gas flow is at orabout the target gas flow temperature and the outlet gas temperature isat or is in excess of the break down temperature of the residualexplosive material present, whereby the internal surface of the sewerline is at or in excess of the break down temperature of the residualexplosive material, the heated flow of gas can be maintained at aboutthat target gas flow temperature for a period of time. The period oftime can be a period of time sufficient to ensure complete breakdown theexplosive material present in the sewer line. This amount of time isreferred to herein as the “soak” time.

Chemical decomposition or break down of the residual explosive materialscan be determined by monitoring the temperature of the heated gas at theburner outlet, or at both the gas inlet and at the gas outlet. Forexample, once the heated flow of gas at the gas inlet is at the targetgas flow temperature, the temperature of the heated flow of gas can beperiodically monitored at the burner outlet, or at both the gas inletand at the gas outlet. As the temperature of the internal surface of asewer line increases, the temperature of the gas exiting the gas outletincreases. Once the outlet gas temperature reaches a temperature at orin excess of the break down temperature of the residual explosivematerial or materials, the heated flow of gas can be maintained at thetarget gas flow temperature for a period of time (soak time).

Sufficient temperatures of gas exiting the sewer line at the gas outlet,depend on the residual explosive material or materials present in thesewer line being decontaminated. For example, an exit gas temperaturecan comprise a temperature of at least about 200° F., of at least about300° F., of at least 400° F., of from about 300° F. to about 3,000° F.,of from about 400° F. to about 3,000° F., of from about 500° F. to about3,000° F., of from about 550° F. to about 3,000° F., of from about 572°F. to about 3,000° F., of from about greater than 572° F. to about2,000° F., or at a temperature greater than about 572° F. Once the exitgas reaches a temperature in excess of the break down temperature, theheated flow of gas can be maintained at the target gas flow temperaturefor a period of time (soak time) sufficient to ensure break down theresidual explosive material.

A sufficient period of time for maintaining the heated gas flow at aboutthe target gas flow temperature to ensure break down of the residualexplosive material can be readily determined by the skilled artisanwithout undue experimentation based on the presently taught parametersincluding, for example, the sewer line material, the internal diameterof the sewer line, the thickness of the sewer line, the length of thesewer line, the flow rate of the heated gas at the target temperature,the target temperature, the temperature of the gas exiting the sewerline at the gas outlet, and the potential amount of, and break downtemperature of, the residual explosive material. For example, as thetarget gas flow temperature and/or flow rate of the heated gas isincreased, the inner surface of the sewer line heats up faster, and thesoak time can be shorter. For example, the longer the length of thesewer line, the greater the amount of soak time that might be required.The greater the temperature of the gas exiting the sewer line at the gasoutlet, the shorter the soak time that might be required.

When the temperature of the outlet gas is at or in excess of the breakdown temperature, the heated flow of gas at the target gas flowtemperature can be maintained for a period of time (soak time)sufficient to ensure complete break down the residual explosivematerial. A sufficient period of time can comprise at least about 1.0hour, at least about 2.0 hours, from about 1.0 hour to about 8.0 hours,from about 1.0 hour to about 6.0 hours, from about 1.0 hour to about 4.0hours, from about 1.5 hours to about 3.0 hours, from about 1.5 hours toabout 2.5 hours, from about 2.0 to about 3.0 hours, or about 2.0 hours.Maintaining the heated flow of gas as described above can ensure thatthe entire internal surface of a sewer line is maintained at or inexcess of the break down temperature of any residual explosive materialor materials present in the sewer line.

According to various embodiments, the heated flow of gas can be providedat a flow rate sufficient to achieve chemical decomposition or breakdown of any residual explosive material or materials present in thesewer line being decontaminated. An appropriate flow rate can be readilydetermined and used by one of ordinary skill to which the presentinvention applies, without undue experimentation, based on theparameters presently taught. Such parameters can include the particularresidual explosive material present, the break down temperature of theresidual explosive material, and/or the composition and physicaldimensions of the sewer line including internal diameter, length, andthickness of the sewer line wall. For example, the flow rate cancomprise a flow rate of from about 100 to about 6,000 cubic feet perminute (hereinafter CFM), of from about 200 to about 5,000 CFM, of fromabout 300 to about 4,500 CFM, of from about 6000 to about 3,000 CFM, orof from about 800 to about 1,200 CFM.

For example, a slower flow rate can be selected for sewer lines having asmaller internal diameter, and a faster flow rate can be selected forsewer lines having a larger internal diameter. For sewer lines having aninternal diameter of from about four inches to about 10 inches, a flowrate of from about 100 to about 2,000 CFM, of from about 200 to about1,500 CFM, or of from about 250 to about 1,000 CFM, can be used. Forsewer lines having an internal diameter of from about 10 inches to about12 inches, a flow rate of from about 500 to about 3,000 CFM, of fromabout 600 to about 2,500 CFM, or of from about 750 to about 1,500 CFM,can be used. For sewer lines having an internal diameter of from about12 inches to about 24 inches, a flow rate of from about 800 to about6,000 CFM, of from about 900 to about 5,500 CFM, or of from about 1,000to about 5,000 CFM, can be used.

According to various embodiments, the flow rate can be adjusted ormodulated during the convective decontamination method according tovarious embodiments of the present teachings. For example, when theheated flow of gas is supplied at an initial temperature lower than thetarget gas flow temperature, the initial flow rate can be slower than atarget flow rate, and the initial flow rate can be increased to thetarget flow rate in accordance with the increase in temperature from theinitial temperature to the target gas flow temperature.

According to various embodiments, a heated flow of gas can be providedto a terracotta sewer line having a length of, for example, from about300 feet to about 400 feet, and having an internal diameter of fromabout 6 inches to about 10 inches. If the sewer line comprises residualexplosive material having a break down temperature of about 572° F.,heated gas can be supplied according to various embodiments at aninitial temperature of from about 100° F. to about 300° F., of fromabout 125° F. to about 225° F., or at about 150° F. The initialtemperature can be slowly increased at a rate of from about 2.0° F./minto about 8.0° F./min, and the target gas flow temperature can be fromabout 575° F. to about 3,000° F. The temperature of the heated flow ofgas at the gas inlet and gas outlet can be periodically monitored. Oncethe temperature of the gas flow at the gas outlet is at or greater thanthe break down temperature, the heated flow of gas entering the inletcan be maintained at about the target gas flow temperature for a soaktime of about 2.0 hours or more.

Referring to FIG. 1, a system 10 is provided. The system 10 can comprisea heated gas flow source 12 comprising a burner unit 14 for producingheated air 16. The burner unit 14 can comprise an ignition device 18,for example, a pilot light and sensor 22, for example, an ultravioletsensor. The heated gas flow source 12 can comprise a blower unit 24 forinducing a flow of heated gas through a sewer line 26 via a gas inlet 28to heat up the sewer line 26, from the burner unit 14 end. The blowerunit 24 can be connected to the burner unit 14 via a flexible duct orhose 30. The heated flow of gas 16 travels from the gas inlet 28 throughthe interior of the sewer line 26 heating an internal surface 32thereof, and exits the sewer line 26 at a gas outlet 34. Residualexplosive contamination is depicted as reference numeral 35. The heatedgas flow source can comprise a fuel source 36 for providing fuel to theburner unit 14. The heated gas flow source can comprise a vaporizer unit38 for vaporizing liquid fuel from the fuel source 36 to produce a gasfuel and for providing it to the burner unit 14. The vaporizer unit 38is in fluid communication with both the fuel source 36 and the burnerunit 14 via a flexible duct or hose 40. Liquid fuel is provided from thefuel source 36 to the vaporizer unit 38 where the fuel is vaporized. Thevaporized fuel is provided to the burner unit 14 where a heated gas isproduced upon combustion.

EXAMPLES Example 1 Thermal Calculations for Convective Heating ofTerracotta Pipes of Various Diameters

The following calculations were performed to illustrate the feasibilityof using convective heat for explosive decontamination. Using thespecific heat of clay used in terracotta sewer line and thermodynamiccalculations, Table II was used to project the theoretical time requiredto raise the temperature of 300 feet of terracotta sewer line to 600°F., at a depth of 0.25 inch into the terracotta material from the insidesurface of the sewer line, using an internal temperature of 1,200° F.The total time represents the time required to reach 600° F. plus atwo-hour soak time. TABLE II THERMAL CALCULATIONS FOR CONVECTIVE HEATINGOF TERRACOTTA PIPES OF VARIOUS DIAMETERS Internal Diameter Time SoakTotal Flow Sample (in.) (min.) (min.) (min.) CFM Total BTU 1 6 100 120220 295  527,968 2 10 70 120 190 820 1,267,449 3 12 65 120 185 1,1801,775,892 4 24 45 120 165 4,700 6,308,770

The above shows that the convective heating method according to variousembodiments of the present teachings is capable of decontaminatingresidual explosive materials contained in a sewer line. Based on thesecalculations, convective heating was then tested in the field.

Example 2 Prepared Test Bed Evaluation

Convective heat treatment was evaluated on a Prepared Test Bedincluding, a 100-foot long length of sewer line. The test bed consistedof 12-inch diameter terracotta pipe and was seeded with explosivematerials at six locations approximately 50, 52, 54, 90, 92 and 94 feetfrom the propane burner. The locations were identified as Prepared TestBed Locations A through F. Each location was seeded with approximatelytwo to three grams of Composition B. The explosive materials containedin Composition B included a mixture of explosive materials. The meltingpoint of Composition B was 378° F. and the deflagration temperature(break down temperature) was 532° F. Locations A and D were seeded withComposition B explosives set into the joint (not covered by soil ormud). Locations B and E were seeded with Composition B and covered topand bottom with soil and set in a joint. Locations C and F were seededwith Composition B and covered top and bottom with mud and set in ajoint. After the test bed was seeded with explosives, the terracottaline was covered with approximately two feet of soil on all sides tosimulate the actual heat sink the convective heat treatment wouldexperience under subsurface conditions.

Hot air for heating the sewer line was generated by burning propane in atube-type burner. The hot exhaust gas from the combustion was directedinto the sewer line to provide thermal energy and heat the line to abovethe deflagration temperatures of the explosive materials present, thatis, above 532° F. The propane fuel was delivered to the site in atrailer-mounted tank. Liquid propane was pulled from the bottom of thetank and then run through a liquid bath vaporizer to change the liquidto a vapor prior to being burned. Ignition of the gas at the burner wasthrough a spark plug igniter. The existence of a flame was determinedwith an ultraviolet sensor (hereinafter “UV” sensor) so that if theflame went out, the supply of propane gas would automatically shut off.Air for combustion was supplied to the burner by a centrifugal blower.The blower was connected to the burner by a spiral-reinforced flexiblehose.

The tube burner was fitted into the end of the sewer line and sealed inplace using mineral wool. The combustion air hose, fuel hose, igniterwire, and UV sensor, were each connected to the burner assembly. Besidesmonitoring the temperatures at the inlet and outlet of the sewer line,temperatures were recorded at 0.25 inch into the terracotta materialfrom the inside surface of the sewer line, 0.50 inch into the terracottaline from the inside surface of the sewer line, and on the outer skin ofthe 1.0 inch thick terracotta line at a location approximately 90 feetfrom the inlet. The temperature was slowly increased by increasing thevolume of propane gas supplied to the burner, to avoid thermal shock tothe terracotta sewer line. Thermal shock can cause a terracotta sewerline to crack and/or collapse. The heated gas flow was started at aninitial temperature of 300° F. At 300° F., some cracking of theterracotta sewer line occurred. To eliminate further cracking of thesewer line, the temperature was reduced to 150° F. and then slowlyincreased.

After completion of the above, the Prepared Test Bed was inspected toconfirm whether the convective heating was effective for explosivedecontamination of sewer lines. It was determined that all of theComposition B explosive material seeded in the sewer line was brokendown during the convective heat treatment.

FIG. 2 is a graph of the temperatures recorded by thermocouples afterthe convective heat treatment of Example 2. In FIG. 2, the “★” symbolrepresents the temperature of the outer skin of the sewer line; the “♦”symbol represents the temperature of the heated flow of gas; the “▪”symbol represents the temperature of the sewer line at a depth of 1.0inch; the “Δ” symbol represents the temperature of the sewer line at adepth of 0.5 inch into the sewer line from the inside surface; and the“x” symbol represents the temperature of the sewer line at a depth of0.25 inch into the sewer line from the inside surface of the sewer line.The “X” axis indicates the time and the “Y” axis indicates temperature.

The seeded explosives were tested for the presence of explosives using acalorimetric reagent and an MO-2M explosive vapor detector. None of thesoils or joints at the seeded locations tested positive for the presenceof explosives. The convective heat treatment successfully decontaminatedexplosive material.

Example 3 Field Evaluation

Convective heat treatment according to various embodiments of thepresent teachings was tested on an existing 365-foot long terracottasanitary sewer line having an eight-inch inner diameter. While runningthe field evaluation on the existing sewer line it became apparent thatgroundwater elevations in the area were above the sewer line, and groundwater was infiltrating into the sewer line. The sewer line at thislocation was between four feet and eight feet below the surface of theground. At the inlet gas flow temperature of 1,200° F., enough heatenergy could not be applied to evaporate all of the infiltratinggroundwater and heat the entire 365-foot length of sewer line.

Thereafter, convective heat treatment according to various embodimentsof the present teachings, was tested on an existing 395-foot longterracotta sanitary sewer line having an eight-inch internal diameter.The sewer line at this location ranged from 10 feet to 16 feet below thesurface of the ground. The sewer line also contained infiltratinggroundwater.

In order to treat the entire length of the sewer line, a hole wasexcavated at approximately the center of the 395-foot long line. Whenthe sewer line was encountered at the bottom of the excavated hole, theeight inch terracotta pipe was broken to form an inlet and access thepipe. This effectively split the sewer line into two lengths, length Aand length B. Two burner units and two blower units were placed in thetwo lengths at the bottom of the excavated hole, and convective heat wasblown in opposite directions (A and B) towards the manholes (outlets).Simultaneously therewith, the burner outlet temperature was slowlyincreased to approximately 2,300° F. instead of 1,200° F. At this rateof energy use, all of the infiltrating groundwater was evaporated, andenough additional energy was supplied to accomplish the goal of raisingthe exhaust temperature to above 572° F. The higher temperature assuredthat the interior surface temperature of the entire length of the sewerline, and any void spaces along the line, were above the break downtemperature.

In addition to monitoring the temperatures at the inlet and outlet ofeach 200-foot length of line lengths A and B, temperatures weremonitored at the outer skin of the one-inch thick terracotta sewer lineat one location in each of lengths, each temperature monitorapproximately 190 feet from the two burners. FIG. 3 illustrates a graphof the temperatures reached during the convective heat treatment.

In FIG. 3, the “♦” symbol indicates the temperature of the heated gasflow in length A; the “▪” symbol represents the temperature of theheated gas flow in length B; the

symbol represents the temperature of the heated gas flow out of lengthA; the “●” symbol represents the temperature of the skin of length B ofthe sewer line; the “Δ” symbol represents the temperature of the skin oflength A of the sewer line; and the

symbol represents the temperature of the heated gas flow out of lengthB. The “X” axis indicates time and the “Y” axis indicates temperature.

To summarize, after evaporating infiltrating ground water, a 395-footsewer line having an eight-inch internal diameter, was successfullydecontaminated. Inlet temperatures were in excess of 2,300° F. withfinal exhaust temperatures of approximately 820° F. Temperatures inexcess of 572° F. were maintained over the entire 395 feet of sewer linefor a soak period of more than two hours.

Other embodiments of the present teachings will be apparent to thoseskilled in the art from consideration of the present specification andpractice of the present teachings disclosed herein. It is intended thatthe present specification and examples be considered as exemplary only.

1. A system comprising: a conduit or vessel comprising an internalsurface including a residual explosive material deposited in or on theinternal surface; and a heated gas flow source in fluid communicationwith the internal surface, wherein the residual explosive material has abreak down temperature and the heated gas flow source is adapted toproduce a flow of heated gas into the sewer line sufficient to heat theinternal surface to a temperature at or in excess of the break downtemperature.
 2. The system of claim 1, wherein the conduit or vesselcomprises a sanitary waste line.
 3. The system of claim 1, wherein theconduit or vessel comprises an industrial pipeline.
 4. The system ofclaim 1, wherein the conduit or vessel comprises a storm water drainline.
 5. The system of claim 1, wherein the internal surface has aninternal diameter of from about one inch to about 100 inches.
 6. Thesystem of claim 5, wherein the inner diameter is from about six inchesto about 36 inches.
 7. The system of claim 1, wherein the residualexplosive material deposited on the internal surface comprises one ormore of nitroguanidine, dinitrotoluene, trinitrotoluene, hexogene,octogene, tetryl, nitrocellulose, nitro-glycerine, ammonium nitrate,lead azide, lead styphnate, and a combination thereof.
 8. The system ofclaim 1, wherein the heated gas flow source comprises a heater to heat agas and a blower to introduce the heated gas into the conduit or vessel.9. The system of claim 1, wherein the heated gas flow source comprises agas burner and a source of an alkane.
 10. The system of claim 9, whereinthe source of an alkane comprises one or more of ethane, propane,butane, pentane, hexane, heptane, octane, and a combination thereof. 11.The system of claim 1, wherein the conduit or vessel comprises an inletand an outlet, the heated gas flow source is in fluid communication withthe inlet, and the heated gas flow source is capable of increasing thetemperature of all points along the internal surface from the inlet tothe outlet, to a temperature at or in excess of the break downtemperature.
 12. The system of claim 1, wherein the heated gas flowsource is capable of producing from about 500,000 British Thermal Units(BTU) to about 10,000,000 BTUs of energy.
 13. The system of claim 1,wherein the heated gas flow source is capable of producing a heated gasat a flow rate of from about 200 cubic feet per minute (CFM) to about5,000 CFM.
 14. The system of claim 1, wherein the heated gas flow sourceis capable of producing a gas flow having a temperature of from about150° F. to about 3,000° F.
 15. The method of claim 14, wherein theheated gas flow source is capable of producing a gas flow having atemperature of from about 1,000° F. to about 3,000° F.
 16. A methodcomprising: connecting a heated gas flow source to a conduit or vessel,the conduit or vessel including an internal surface and comprisingresidual explosive material deposited in or on the internal surface, theresidual explosive material having a break down temperature at which theresidual explosive material chemically breaks down; introducing a heatedgas flow into the conduit or vessel; and maintaining a heated gas flowinto the conduit or vessel at least until the temperature of theinternal surface reaches a temperature at or in excess of the break downtemperature.
 17. The method of claim 16, wherein the heated gas flow isintroduced at a temperature of from about 150° F. to about 3,000° F. 18.The method of claim 16, wherein the heated gas flow is introduced at atemperature of from about 1,000° F. to about 3,000° F.
 19. The method ofclaim 16, wherein the conduit or vessel comprises at least one inlet andat least one outlet, the heated gas flow is introduced at the at leastone inlet, and the heated gas flow has a temperature at the outlet of atleast about 200° F.
 20. The method of claim 16, further comprisingproducing the heated gas flow by burning a fuel in the presence ofoxygen gas.
 21. The method of claim 16, wherein the heated gas flowcomprises heated air and combustion products.
 22. The method of claim16, wherein the conduit or vessel comprises a sewer line.
 23. The methodof claim 16, wherein the conduit or vessel comprises an aboveground orunderground storage tank.
 24. A method, comprising: providing a heatedgas flow at an initial temperature to a conduit or vessel that comprisesan inlet, an outlet, and an internal surface, the internal surfacecomprising residual explosive material having a break down temperature,deposited at least therein or thereon, the internal surface being influid communication with the heated gas flow; and maintaining the heatedgas flow at or above the initial temperature at least until thetemperature of the heated gas flow at the outlet is at or above thebreak down temperature of the residual explosive material.
 25. Themethod of claim 24, further comprising periodically monitoring thetemperature of the heated gas flow at the inlet, at the outlet, or atboth the inlet and the outlet.
 26. The method of claim 24, furthercomprising increasing the initial temperature to a target temperaturethat is at or above the break down temperature of the residual explosivematerial.